Tachometer acting funny

[KCshorty]

My tachometer is acting funny. It bounces (needle jumps around) around and is not giving an accurate reading. I have already checked all the connections in back of the gauge cluster. I can only suspect that it is the sending unit. Can anyone tell me what sensor sends the signal to the tachometer? I checked the FSM, but can’t seem to figure it out.

[driverdriver]

The whole instrument cluster is known to fail after so many years. Problems start at either the odometer or tachometer. First step is to pull the instrument cluster out and clean the contacts and re-plug and see if the problem disappears.

[swimshark]

Does it bounce around like it is broken or if a sensor isnt reading properly?

[KCshorty]

The whole instrument cluster is known to fail after so many years. Problems start at either the odometer or tachometer. First step is to pull the instrument cluster out and clean the contacts and re-plug and see if the problem disappears.

I have taken out the cluster and cleaned each contact with no residue electronics cleaner and then reassembled. It did not seem to have an effect on the problem.

One thing i do know is that it used to happen only occasionally. Now it happens all the time. It used to go away after the car was driven for long distances and also when the A/C was on. Now it seems to appear every time the car is driven, no matter how long the trip or with A/C being on.

[KCshorty]

Does it bounce around like it is broken or if a sensor isnt reading properly?

How do i tell? It's acting to me like it is getting a faulty signal. Seems to be getting some kind of signal because its "jumping",even when the car is parked and not moving. So that is why i was thinking sensor.

Does anyone know if you can test the tachometer to see if that is the problem? I have a multimeter,just not sure how to test and what numbers would be within or outside spec.